AP BIOLOGY

Detailed explanation-1: -Receptors are protein molecules inside the target cell or on its surface that receive a chemical signal. Chemical signals are released by signaling cells in the form of small, usually volatile or soluble molecules called ligands.

Detailed explanation-2: -Receptors are protein molecules in the target cell or on its surface that bind ligands. There are two types of receptors: internal receptors and cell-surface receptors.

Detailed explanation-3: -Receptor proteins are transmembrane proteins. Transmembrane receptor proteins are embedded in the phospholipid bilayer of the PM with a hydrophobic region of the protein spanning the bilayer and hydrophilic regions extending out on both the intracellular (cytoplasmic) and extracellular sides of the membrane.